As information-handling systems become more complex, and require more information to be handled at greater speeds, they need components of more compact size, greater capacity, and faster speeds. It is widely believed that optoelectronic components are particularly promising for use in such systems because optics offers considerable advantages over pure electronics as a communication medium, as data rates move into the gigabit range. For example, it now appears that free space optics offers considerable advantages over wire leads for the interconnection of processing elements in computer systems that use closely spaced semiconductive chips as the processing elements, as in computers that involve massively parallel computation.
Such optical interconnection networks depend importantly on optical components that are compact, rugged, efficient and scalable for use in large systems. The present invention is directed at providing such apparatus.
The present invention in its preferred embodiments focuses particularly on devices adapted to function in a parallel computation system of the kind described in our copending application, Ser. No. 07/994,220, filed Dec. 18, 1992 having the same assignee as this application. However, such devices should also be useful in various other forms of high speed information handling systems.
In that application, there is described a parallel processing system that divides the processing elements into clusters and includes an interconnect network that is of a three-stage modified-close type. It uses electronic switches in the first and third stages for switching between processing elements in a common cluster and optoelectronic switches to switch between clusters in the second stage that use free-space light beams for use as the transmission medium between clusters. This system is designed so that generally only two routing decisions need to be made in interconnecting any two processing elements. The present invention provides components that are particularly well adapted for use in the second stage of such a system. Reference can be made to such copending application for a more detailed description.
In such a system, the second stage comprises a plurality of lasers that serve as transmitters and a plurality of photodetectors that serve as receivers, the communications therebetween being by light beams that originate from the lasers and terminate at the photodetectors, the routing therebetween being done by various optical elements.
For such communication, an optoelectronic switch is advantageously employed by means of which one laser in an array of lasers is selectively energized by a transmitting processing element, the selection being dependent on the cluster to which belongs the photodetector of the processing element intended as the destination of the information being transmitted.
In one aspect, the present invention is a device that serves as a suitable optoelectronic switch that permits such selection.
Advantageously, each processing element includes both an information processor and a routing portion and all the routing portions in a cluster are interconnected by way of a local switch that permits each processing element to communicate with all other processing elements in a cluster.
Additionally, information that is generated in the information processor of a processing element and intended for transfer to a different cluster may be transferred by way of its routing portion to the routing portion of a different processing element in the same cluster for transfer by the optical interconnection network.
As a consequence, each routing portion has available to it, for transfer by the optical interconnection network, information from the information processor of each of the processing elements in the cluster.
By use of the routing portions, it becomes possible to couple the information from any processing element of the cluster to any optoelectronic switch in the same cluster.
In a similar fashion, advantageously each photodetector in a cluster is coupled to a routing portion of a processing element, and so can couple to the routing portion of any processing element in the cluster, whereby the information received by the photodetector in the cluster can be transferred to any processing element in the cluster for use by it.
Moreover, a light beam, in its routing from the laser associated with the cluster of the transmitting processing element to the photodetector associated with the cluster of the receiving processing element, may experience considerable attenuation since such routing may involve passage through a number of microlenses and reflection from a number of partially transmissive mirrors.
Accordingly, in another aspect, the present invention is a regenerator that can be inserted in the path of a weak light beam and then used to intercept the light beam, amplify or regenerate it, and send it along on a path that is collinear with the path from which the beam was initially intercepted.